1. Field of the Invention
The invention relates to a contact element between housing parts, wherein at least one of the housing parts is formed of a sheet metal and a sheet metal tab, formed as a unitary part of this sheet metal, forms the springy contact element, wherein the sheet metal tab with its base adjoins a sheet metal edge and rests electrically conductingly against the other housing part by means of a contact surface positioned at a spacing to the base, wherein the sheet metal tab is reduced in its thickness in a section between the sheet metal edge and the contact surface relative to the thickness of the sheet metal by cold forming.
2. Description of the Related Art
Such a contact element is known from DE 195 07 846 C1 and has excellent spring properties which ensure a safe electrical contacting between the housing parts for obtaining electromagnetic shielding. Such contact elements can be formed during the manufacture of the housing parts without great manufacturing expenditure.
In order to ensure a sufficient spring travel without permanent deformation of the contact elements, they must have a corresponding length. A correspondingly matched large rectangular cutout or notch must be provided within the sheet metal into whichxe2x80x94viewed from the narrow sidexe2x80x94the sheet metal tab projects. By means of cold forming, the deep-drawable sheet metal in the area of the sheet metal tab is reduced in its thickness so that the sheet metal tab has spring properties. For correspondingly long sheet metal tabs sufficient spring travel is ensured which ensures a safe contacting even after several mounting and demounting operations of the housing parts.
Modern housings are becoming smaller and smaller. The continuing miniaturization enables extremely flat built-in parts. The housing sidewalls therefore are very narrow so that problems result in regard to providing contact elements in the area of the housing sidewalls. Large window-shaped cutouts for providing the required spring lengths weaken the housing sidewalls; sheet metal tabs which are too short have only minimal spring properties and have the tendency to be permanently deformed so that after several mounting and demounting operations of a housing a safe electrical contacting is no longer ensured.
It is an object of the invention to develop a contact element of the aforementioned kind such that a weakening of the housing sidewalls is substantially prevented while providing sufficient spring properties.
This object is solved according to the invention in that the base, at least at the level of the sheet metal edge, is wider than the width of the sheet metal tab itself measured in the transverse direction, and in that the cold-formed section extends past the base and the sheet metal edge into the sheet metal itself.
The base of the sheet metal tab, with which it adjoins the edge of the cutout, is configured to be wider than the sheet metal tab itself wherein the cold-formed section projects past the base and the sheet metal edge into the sheet metal itself so that a continuous transition of the cold-formed section out of the sheet metal into the sheet metal tab is provided. The constructive extension of the deformation section past the base into the sheet metal also enables, even for short sheet metal tabs, great spring properties without this resulting in the risk of a permanent deformation because of spring travel that is too great. The configuration of the deformed section so as to extend into the sheet metal thus enables short free lengths of the sheet metal tabs; correspondingly, the cutouts, in which the sheet metal tabs are positioned, can be made very short in the longitudinal direction of the sheet metal tabs.
While, for example, according to DE 195 07 846 C1, sheet metal tabs of a minimum of 15 to 16 mm are required in order to provide satisfactory spring properties, sheet metal tabs can be manufactured according to the invention with a minimal length of approximately 8 mm and sufficient spring properties. When optimizing the constructive configuration, minimal lengths of 5 to 6 mm are possible so that the required window-like cutouts can be kept very small. In this way, a weakening of the housing sidewalls is prevented as much as possible.
Preferably, the sheet metal tab adjoins the sheet metal edge via a base section which widens in the direction toward the sheet metal edge so that in this area a sufficient amount of material is available which is provided with spring properties by cold forming and ensures the required spring elasticity of the contact element. Preferably, for this purpose the base section has approximately a basic shape of a trapezoid in a plan view, wherein the larger one of the base sides of such a basic shape of a trapezoid is positioned at the level of the sheet metal edge.
For obtaining a sufficient spring elasticity, the base section is deformed about its entire width; in this connection, the end section of the deformation section tapering off within the sheet metal can be deformed or shaped with the same width as the base; preferably, the end section of the deformation section in the sheet metal is configured to be wider than the base.
The end section of the deformation section tapering off within the sheet metal has expediently an extension measured in the direction of the longitudinal center axis of the sheet metal tab, which extension is approximately 20 to 50%, in particular, 35%, of the free length of the deformation section.